Ostomy device with a switchable adhesive layer located between a backing layer and an absorbent adhesive layer

ABSTRACT

An ostomy device has a switchable adhesive layer located between a backing layer and an absorbent adhesive layer. The switchable adhesive layer has a photoinitiator reactive to visible light and the absorbent adhesive layer is a skin-facing layer having absorbent particles.

Disclosed is an ostomy device with an adhesive wafer for attachment to askin surface of a user and a collecting bag connected to the adhesivewafer. The adhesive wafer includes a backing layer, a switchableadhesive composition, an absorbent adhesive composition, and a releaseliner.

BACKGROUND

In connection with surgery for a number of diseases in thegastro-intestinal tract, one of the consequences in many cases is thatthe patient is left with an abdominal stoma, such as a colostomy, anileostomy or a urostomy, in the abdominal wall for the discharge ofvisceral contents. The discharge of visceral contents cannot beregulated at will. For that purpose, the user will have to rely on anappliance to collect the material emerging from such opening in a bag,which is later emptied and/or discarded at a suitable time. Ostomyappliances are typically attached to the skin of the ostomy user bymeans of an adhesive wafer on the ostomy appliance.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated into and a part ofthis specification. The drawings illustrate embodiments and togetherwith the description serve to explain principles of embodiments. Otherembodiments and many of the intended advantages of embodiments will bereadily appreciated as they become better understood by reference to thefollowing detailed description. The elements of the drawings are notnecessarily to scale relative to each other. Like reference numeralsdesignate corresponding similar parts.

In FIG. 1 is shown schematically in cross section view an adhesive waferwith a bevelled second adhesive.

In FIG. 2 is shown schematically in cross section view an adhesive waferwhere detachment from the skin is initiated.

In FIG. 3 is shown a schematic cross-section view of the second adhesivelayer.

In FIG. 4 is shown schematically in perspective view a test sample ofthe second adhesive.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments provide an ostomy device comprising an adhesive wafer forattachment to a skin surface of a user, and a collecting bag forcollecting output from a stoma, the bag being connected to the adhesivewafer; the adhesive wafer having a through-going hole for accommodatingthe stoma of the user; and the adhesive wafer comprising a backinglayer, a first switchable adhesive layer, a second adhesive layer, and arelease liner, the first adhesive layer at least partly overlying asecond adhesive layer, wherein the second adhesive layer has a centralportion with a first thickness and an outer edge portion with a secondthickness, the first thickness being larger than the second thickness.

In embodiments, the adhesive wafer will have a proximal (“skin-facing”)surface, which faces the skin of the user during use, and a distal(“non-skin-facing”) surface, which faces away from the user's skinduring use. Before use, the proximal surface of the adhesive wafer canbe covered by a release liner, which is releasably attached to theadhesive. The release liner can be removed by the user immediately priorto application of the adhesive wafer to the skin. Both before and duringuse, the distal surface of the adhesive wafer can be made up of abacking layer, which can be used to attach the collecting bag to theadhesive wafer, for instance by welding. As such, the adhesive wafer maycomprise a distal backing layer and a proximal release liner, with thefirst switchable adhesive composition and the second absorbent adhesivecomposition located between the backing layer and the release liner.

The adhesive wafer includes a first switchable adhesive composition.Switchable means that the adhesive can be switched between at least twodifferent states with different properties.

The switch is the transition from one state to another state of aswitchable composition. The duration of the switch will vary dependingon, e.g., the nature of the switch initiator and the method ofactivation of the switch initiator. Generally, the switch will be agradual process with a gradual change of physical properties of thematerial from one state to another state. In some instances, the switchwill be very fast and the physical properties will change very quickly,e.g. within seconds, to those of the second state. In other instances,the switch will be slower and the change in properties will happengradually over a period of, e.g., several minutes or even hours.

In embodiments, the switchable adhesive composition can be switched froma tacky state to a non-tacky or low-tack state in which the switchedadhesive has a reduced peel strength relative to the peel strength ofthe adhesive before switching.

Since the switchable adhesive composition can be switched to a non-tackyor low-tack state, it can initially be provided in a high-tack statewith a tack that would otherwise not be suitable for use on skin becauseit would be too difficult or too painful to remove. In other words, thepre-switch tack can be very high because it is not required that theadhesive can be removed again from the skin in the pre-switch state. Inthis manner, the switchable adhesive composition can be made to have apre-switch application state, in which the properties are suitable forapplication to the skin of the user, and a post-switch removal state, inwhich the properties are suitable for removing the adhesive from theskin.

Recognizing that the expression “low-tack” is a relative term, it willbe defined here as meaning the condition of minimum tackiness which theadhesive reaches after switching from its tacky state. The reduction inpeel force may be as great as 100% or as little as 30%. In embodiments,the reduction in peel force is 30-40%, 30-50%, 30-60%, 30-70%, 30-80%,30-90%, 30-100%, 40-50%, 40-60%, 40-70%, 40-80%, 40-90%, 40-100%,50-60%, 50-70%, 50-80%, 50-90%, 50-100%, 60-70%, 60-80%, 60-90%,60-100%, 70-80%, 70-90%, 70-100%, 80-90%, 80-100%, or 90-100%. Inembodiments, the reduction in peel force is at least 50%.

The adhesive wafer includes a second adhesive composition. The secondadhesive composition may be an absorbent adhesive. The absorbentadhesive composition is capable of absorbing moisture. The purpose ofhaving an absorbent adhesive composition as a part of an ostomy deviceis to allow the absorbent adhesive composition to absorb moistureproduced by the skin and thereby prevent accumulation of moisture at theskin surface, underneath the ostomy device. Accumulation of moisture onthe skin surface can lead to damage of the skin, such as maceration.

By providing an adhesive wafer having both a switchable adhesivecomposition and an absorbent adhesive composition, the present inventorshave been able to construct an ostomy device, which can adhere quicklyand strongly to the skin of the user and at the same time properlyabsorb moisture to prevent damage to the skin underneath the adhesive.The fast and strong adhesion to the skin effected by the switchableadhesive composition further leads to prevention of leakage of outputfrom the ostomy.

Furthermore, when combining a switchable adhesive with an absorbentadhesive, problems may occur during detachment of the wafer. First stepof removal is to switch the switchable adhesive by exposing it to light(or other stimuli). This will turn the adhesive from highly tacky to avery low tack. The second adhesive, not being switchable, maintains itstackiness to the skin. When the wafer is peeled off the skin by grippingthe edge portion of the wafer (the first adhesive) and pulling, thefirst adhesive will come off easily, being switched into a low tackstate, whereas the second adhesive still maintains good adhesion to theskin. Thus, there is a risk that the wafer will delaminate such that thefirst switchable adhesive will come off the skin and delaminate from thesecond adhesive, whereas the second absorbent adhesive may remain whollyor partially on the skin. Having the second absorbent adhesive remainattached to the skin or having residue from the second absorbentadhesive stuck to the skin after removal of the rest of the adhesive isa highly undesirable situation.

By using a switchable adhesive composition with a pre-switch high-tackstate, a quick initial adherence between the adhesive and the skin ofthe user can take place. Such a quick and strong adhesion will, alreadyfrom application of the adhesive to the skin, prevent output fromleaking into the space between the skin and the adhesive. This is incontrast to some non-switchable pressure sensitive adhesives, whichtypically require a significant amount of time, such as 10-60 minutes,to achieve strong adhesion. By applying pressure to the pressuresensitive adhesive it is possible for the adhesive to wet and flowfaster into the skin surface, hereby obtaining a large contact area andhereby increasing the adhesive power. Some current adhesive systems forattachment of ostomy device to the skin require a high or prolongedpressure from the user in order to sufficiently flow into and wet thesurface of the substrate. By using a switchable adhesive with an initialhigh tack, neither a high pressure nor a long time is needed in order toensure a good and enduring adhesion to the skin.

In addition to the early formation of a strong adhesive bond, theswitchable adhesive also makes it possible to maintain a very strongadhesive bond during the entire period of use of the ostomy device. Thisis because it is not necessary to be able to remove the adhesive in thepre-switched state. Therefore, the adhesion to the skin in thepre-switched state can remain very high right up until the switch causesthe adhesion to drop significantly, thus allowing easy and pain-lessremoval of the device.

In embodiments, the first switchable adhesive composition is in contactwith the backing layer. The first switchable adhesive composition may bedisposed on the backing layer or coated on the backing layer. By beingin contact with the backing layer, at least part of the switchableadhesive composition is close to the distal non-skin-facing surface ofthe adhesive wafer. This will make it easier to effect the switch of theswitchable adhesive composition, for instance by applying light to theswitchable adhesive composition through the backing layer.

In embodiments, the release liner is in contact with both the firstswitchable adhesive composition and the second absorbent adhesivecomposition. The release liners covers the surface of the adhesive thatis to be attached to the skin of the user. As such, the surface of theadhesive that is in contact with the release liner is also the surfacethat will be in contact with the skin of the user during use. By havingboth the first switchable adhesive composition and the second absorbentadhesive composition form part of the adhesive surface that comes intocontact with the user's skin, it is ensured that both adhesives canexert their respective effects directly on the skin. In other words,both adhesive compositions will be in contact with the user's skinduring use. The switchable adhesive composition can cause the rapid,strong, and enduring adhesion to the skin and the absorbent adhesivecomposition can ensure that moisture is effectively removed from thesurface of the skin.

In embodiments, the second absorbent adhesive composition is locatedbetween the first switchable adhesive composition and the release liner.The absorbent adhesive composition can cover a part of the surface ofthe switchable adhesive composition on the proximal skin-facing side ofthe adhesive wafer. The switchable adhesive composition can cover theentire distal non-skin-facing surface of the absorbent adhesivecomposition. By such an arrangement, the absorbent adhesive will comeinto contact with the skin of the user and can thereby easily absorbmoisture from the skin surface. None of the switchable adhesive will becovered on the distal non-skin-facing surface by the absorbent adhesive,thus making it easier to effect the switch by, for instance, shininglight on the switchable adhesive without having to have the light passthrough the absorbent adhesive.

In embodiments, the adhesive wafer has a central part adjacent to thehole for accommodating the stoma and a peripheral part adjacent to anedge of the adhesive wafer away from the hole. The second absorbentadhesive composition may be located at least in the central part of theadhesive wafer. The central part of the wafer is the part that is closerto the through-going hole in the wafer than it is to the peripheral edgeof the wafer. Typically, this will represent a ring-shaped area of theadhesive wafer surrounding the hole. The central part will be the partof the wafer that is closest to the stoma during use of the ostomydevice. The peripheral part is the remainder of the adhesive waferoutside the central part, i.e., the part that is closer to theperipheral edge than to the hole. Typically, the peripheral part willalso be a ring-shaped area of the adhesive wafer. The absorbent adhesivemay be in the entire central part of the wafer or only in part of thecentral part. The absorbent adhesive may extend also to the peripheralpart of the adhesive wafer. By being in the central part of the adhesivewafer, the absorbent adhesive will be located close to the stoma andwill thereby be close to the sensitive skin surrounding the stoma. Thiswill allow the absorbent adhesive to absorb moisture form the sensitiveskin around the stoma. Also, an absorbent adhesive may be able to swellduring use as a consequence of the absorption of moisture and may thusbe able to increase in volume and provide a mechanical sealing aroundthe stoma.

In embodiments, the second absorbent adhesive composition is locatedonly in the central part of the adhesive wafer. The absorbent adhesivecomposition may be located as a ring-shaped element in the central partof the adhesive wafer, thus surrounding the stoma during use.

In embodiments, the first switchable adhesive composition is located atleast in the peripheral part of the adhesive wafer. The switchableadhesive composition may be in the entirety of the peripheral part oronly in part of the peripheral part of the wafer. The switchableadhesive composition may extend into the central part of the wafer.

In embodiments, the releaser liner is in contact with the firstswitchable adhesive composition in the peripheral part of the adhesivewafer. In this manner, the switchable adhesive will be in contact withthe skin at the peripheral part of the adhesive wafer during use. Byhaving the switchable adhesive composition in the peripheral part incontact with the skin during use, a strong adhesive bond is establishedaround the periphery of the adhesive wafer, thus making it less likelythat the adhesive wafer will start to peel off due to contact with thesurroundings, such as the user's clothes.

In embodiments, the releaser liner is in contact with the secondabsorbent adhesive composition in the central part of the adhesivewafer. In this manner, the absorbent adhesive will be in contact withthe skin surrounding the stoma during use. This will allow the absorbentadhesive to absorb moisture directly from the sensitive skin surroundingthe stoma, thereby preventing damage to the skin, such as maceration.

In embodiments, the backing layer is suitably elastic, i.e. it has a lowmodulus, enabling the adhesive construction to conform to the skinmovement and provide comfort when using it. The backing layer may have astructured surface to improve the adhesion between the adhesive and thebacking layer. The backing layer may be a non-woven or a non-woven-filmlaminate. The backing layer may be a polymer film. The backing layer maycomprise polyurethane. The thickness of the backing layer is dependenton the type of backing layer used. For polymer films, such aspolyurethane films, the overall thickness may be between 10 to 100micrometers, such as between 10 to 50 micrometers, such as about 30micrometers.

The release liner may be of any material known to be useful as a releaseliner for medical devices. For instance, the release liner may be in theform of a polymer film, foil, or paper, having release properties thatenable the adhesive to be released easily from the liner. Suchproperties may be inherent in the material or the layer may besiliconized, coated with a low surface tension coating, or subjected toother appropriate surface modifications. Release liners are in generalmade on a mechanically stiff backing such as paper, polyethylene,polypropylene, or polyethylene terephthalate. This stiffness willsupport the adhesive wafer when applying the collecting device.

In embodiments, the second absorbent adhesive composition is in the formof a ring-shaped adhesive element located around the hole in theadhesive wafer and in contact with the release liner. Such a ring-shapedabsorbent adhesive element could have a diameter of 30-70 mm, such as40-70 mm, such as 50-70 mm, such as 60-70 mm. The ring-shaped adhesiveelement could for instance have a diameter of 30 mm, 40 mm, 50 mm, 60mm, or 70 mm. The ring shaped element could have a width, i.e. thedistance from the inner rim of the ring to the outer rim of the ringmeasured along the surface of the ring, of at least 10 mm, at least 20mm, at least 30 mm, at least 40 mm, at least 50 mm, 10-20 mm, 10-30 mm,10-50 mm, 20-30 mm, 20-40 mm, 20-50 mm, 30-40 mm, 30-50 mm, or 40-50 mm.The width of the element can be constant over the entire element or itmay vary.

In embodiments, the first switchable adhesive composition extends in theentire area of the adhesive wafer. In embodiments, the first switchableadhesive composition is in the form of a ring-shaped adhesive elementlocated at the periphery of the adhesive wafer. Such a ring-shapedswitchable adhesive element could have a diameter of 50-150 mm, such as50-120 mm, such as 50-100 mm, such as 50-75 mm. The ring-shaped adhesiveelement could for instance have a diameter of 50 mm, 60 mm, 70 mm, 80mm, 90 mm, 100 mm, 120 mm, or 150 mm. The ring shaped element could havea width of at least 10 mm, at least 20 mm, at least 30 mm, at least 40mm, at least 50 mm, at least 60 mm, at least 70 mm, at least 80 mm, atleast 90 mm, at least 100 mm, 10-20 mm, 10-30 mm, 10-50 mm, 10-100 mm,20-30 mm, 20-40 mm, 20-50 mm, 20-100 mm, 30-40 mm, 30-50 mm, 30-100 mm,40-50 mm, 40-100 mm, or 50-100 mm. The width of the element can beconstant over the entire element or it may vary.

By the term “ring-shaped” is herein understood that the adhesive definesa band circumferending the central opening. The outline of this band maybe substantially circular, oval or other rounded shape. An adhesiveelement could also have an only roughly ring-shaped, oval, or roughlyoval form. In that case, the mentioned diameters would be the maximumdistance from one point on the outer edge of the element to anotherpoint on the outer edge of the element.

In embodiments, the second absorbent adhesive composition has a firstthickness in the central portion, i.e. the distance from one outersurface of the adhesive to the other outer surface of the adhesivemeasured in a straight line perpendicular to the surface of theadhesive. In embodiments, the first thickness of the absorbent adhesivecomposition is at least 50 micrometers, such as at least 100micrometers, such as at least 200 micrometers, such as at least 300micrometers, such as at least 400 micrometers, such as at least 500micrometers, such as at least 750 micrometers, such as at least 1,000micrometers. The first thickness of the absorbent adhesive compositionmay be between 50 micrometers and 1,000 micrometers, such as 100-500micrometers, such as 200-400 micrometers, such as 200-300 micrometers.The uniform thickness of the absorbent adhesive composition may be50-250 micrometers, 100-250 micrometers, 250-500 micrometers, 250-750micrometers, 500-750 micrometers, 500-1,000 micrometers, 500-1500micrometers, 500-200 micrometers, 1000-2000 micrometers.

In embodiments, the first switchable adhesive composition has a uniformthickness. In embodiments, the uniform thickness of the absorbentadhesive composition is at least 10 micrometers, such as at least 25micrometers, such as at least 50 micrometers, such as at least 100micrometers, such as at least 200 micrometers, such as at least 300micrometers, such as at least 400 micrometers, such as at least 500micrometers, such as at least 750 micrometers, such as at least 1,000micrometers. The uniform thickness of the absorbent adhesive compositionmay be between 10 micrometers and 1,000 micrometers, such as 25-500micrometers, such as 50-500 micrometers, such as 100-500 micrometers,such as 200-400 micrometers, such as 200-300 micrometers. The uniformthickness of the absorbent adhesive composition may be 10-50micrometers, 10-100 micrometers, 25-50 micrometers, 25-100 micrometers,50-100 micrometers, 50-250 micrometers, 100-250 micrometers, 250-500micrometers, 250-750 micrometers, 500-750 micrometers, 500-1,000micrometers, 500-1500 micrometers, 500-200 micrometers, 1000-2000micrometers.

In embodiments, the first switchable adhesive composition has a variedthickness. In embodiments, the maximum thickness of the absorbentadhesive composition is at least 10 micrometers, such as at least 25micrometers, such as at least 50 micrometers, such as at least 100micrometers, such as at least 200 micrometers, such as at least 300micrometers, such as at least 400 micrometers, such as at least 500micrometers, such as at least 750 micrometers, such as at least 1,000micrometers. The maximum thickness of the absorbent adhesive compositionmay be between 10 micrometers and 1,000 micrometers, such as 25-500micrometers, such as 50-500 micrometers, such as 100-500 micrometers,such as 200-400 micrometers, such as 200-300 micrometers. The maximumthickness of the absorbent adhesive composition may be 10-50micrometers, 10-100 micrometers, 25-50 micrometers, 25-100 micrometers,50-100 micrometers, 50-250 micrometers, 100-250 micrometers, 250-500micrometers, 250-750 micrometers, 500-750 micrometers, 500-1,000micrometers. In embodiments, the first switchable adhesive compositionis thicker in the peripheral part of the adhesive wafer than in thecentral part of the adhesive wafer. In embodiments, a thickness of thefirst switchable adhesive composition in the peripheral part of theadhesive wafer is at least 120%, such as at least 150%, such as at least200%, such as at least 250%, such as at least 500% of a thickness of thefirst switchable adhesive composition in the central part of theadhesive wafer.

In embodiments, the switchable adhesive composition is disposed on thebacking layer and covers the entire backing layer. The absorbentadhesive composition is in the form of a ring-shaped adhesive element inthe center of the adhesive wafer around the hole and on the skin-facingsurface of the switchable adhesive composition. In this manner, theswitchable adhesive composition will be in contact with the releaseliner in the periphery of the wafer and the absorbent adhesivecomposition will be in contact with the release liner in the center ofthe wafer. Both adhesives will therefore be in contact with the skin ofthe user during use.

In embodiments, the skin-contacting surface of the adhesive wafer isconstituted by the second adhesive at the central portion of the waferand the first adhesive at the peripheral portion of the wafer. Suchconstruction may provide sealing and moisture handling next to the stomaand a strong attachment to the skin along the periphery, therebydecreasing the risk of rolling up of the edge portion as well asleakage.

Traditional peel tests are performed by peeling an adhesive substratefrom a steel plate or other stiff substrate. However, peel from skin isquite different from steel as the skin is soft and flexible and willstretch and follow the adhesive in the pull direction, therebydistributing the forces in the substrate in a different way. So, anadhesive wafer construction may show promising results withoutdelamination when peeled from a stiff substrate, whereas peeling thesame device from skin may result in delamination.

In embodiments, a bevelled edge can be described as an adhesive layerwith a thickness of the central portion of one thickness and anotherthickness at the edge portion. The thickness decreases over a distancethereby providing a sloping line between the central and the edgeportion. This line defines an angle with the plane of the adhesivelayer. The angle may be 10-60 degrees, such as 15-50 degrees, such as20-40 degrees or even 20-30 degrees. The thickness at the edge maydetermine the degree of delamination.

The edge portion of the second adhesive may be bevelled. By bevelled isherein meant that in a cross-section of the edge portion it defines asloping line from the portion of the first thickness to the portion ofthe second thickness. The line may be linear or curvilinear.

The edge portion of the second adhesive may be bevelled in an angle of10 to 60 with respect to the surface of the second adhesive layer.

The second thickness of the second adhesive may be less than 300 μm. Thesecond thickness may define a rim portion of the second adhesive layer.The lower the second thickness is, the less prone is the wafer todelaminate when removed from the skin.

In embodiments, the first switchable adhesive composition comprisescurable molecules selected from the group consisting of acrylic acidesters or methacrylic acid esters of alcohols, glycols, pentaerythritol,trimethylpropane, glycerol, aliphatic epoxides, aromatic epoxidesincluding bisphenol A epoxides, aliphatic urethanes, silicones,polyesters and polyethers.

In embodiments, the first switchable adhesive composition comprises apolymer selected from the group consisting of polyacrylates,polyurethanes, and polysilicones.

In embodiments, the first switchable adhesive composition comprises aphotoinitiator. A photoinitiator makes it possible to switch theadhesive composition by activating the photoinitiator with light.Different photoinitiators have different absorption spectra and willneed to be activated by light in different wavelengths. In embodiments,the first switchable adhesive composition comprises a photoinitiatorreactive to visible light. This will make it possible to cause theswitch of the adhesive by applying regular visible light. This is a safeand convenient method of switch, especially if the switch is to beeffected by the user of the ostomy device.

In some embodiments, the light comprises visible light and/orultraviolet (UV) light. Visible light is defined as electromagneticradiation with a wavelength in the range 400-700 nm. Ultraviolet lightis defined as electromagnetic radiation with a wavelength in the range10-400 nm. In embodiments, the photoinitiator will be reactive toultraviolet light.

In embodiments, the first switchable adhesive composition comprises aphotoinitiator selected from the group consisting of titanocenephotoinitiators; dye/co-initiator systems includingthionine/triethanolamine; dye/borate salt systems; dye/peroxide systemsand 1,2-diketone/co-initiator systems, includingcamphor-quinone/tertiary amine.

In embodiments, the switchable adhesive composition may be absorbent asdescribed herein for the absorbent adhesive composition.

In embodiments, the switchable adhesive composition is a switchablepressure sensitive adhesive (PSA) composition. The switchable PSA maycomprise a mixture, in proportions by weight, of 2% to 80% of curablemolecules that are curable by free radical polymerisation, 0.05% to 10%of photoinitiator and an internal cross-linker that is cross-linkable bymechanism other than free radical polymerisation for cross linking theadhesive, the balance being base adhesive polymer and incidentalconstituents and the weight proportions being calculated on the basis ofthe dry weight of the base adhesive polymer. The PSA may have a cohesivestrength of between 5 and 100 N/12.7×12.7 mm measured according to FINATtest method No. 18 The cohesive strength may be significantly higherthan 30N/12.7×12.7 mm depending on the application for which theswitchable PSA is intended. Preferably, the base adhesive polymer andcurable molecules are mutually soluble when dry, although good resultsare still obtained when the curable molecules are uniformly dispersed inthe adhesive even when the adhesive and curable molecules are mutuallyinsoluble or only partly mutually soluble when dry. The cohesivestrength of the composition is determined by controlling the cohesivestrength of the adhesive polymer backbone, and this is done by partiallycross-linking it.

Cross-linking can be achieved by incorporating monomers of e.g.N-methylol acrylamide, N-(iso-butoxymethylene)acrylamide, methylacrylamidoglycolate methyl ether (all 0.5-5%) or metal chelates, e.g.,acetylacetonates of Zr, Al, or Fe (up to 2% of polymer weight) into thepolymer backbone which then cross-links during drying after spreading ona substrate.

Al and Ti acetylacetonates and similar compounds can also be added afterthe polymerization step in concentrations between 0.1 and 2% of thepolymer weight and used as an internal cross-linker through utilizingcarboxylic groups in the polymer backbone during the drying step.

Multi-functional isocyanates like toluene diisocyanate (TDI), trimethylhexamethylene diisocyanate (TMDI), hexamethylene diisocyanate (HDI), orisophorane diisocyanate (IPDI), can be used to chemically inter linkhydroxylic or carboxylic functions of different polymer chains, added inconcentrations up to about 1% of the polymer weight.

Internal cross-linking can also be achieved between the carboxylicgroups in the polymer backbone and added amino resins such as melamine,benzoguanamine, glycoluril, urea derivatives e.g. hexamethoxymethylmelamine, methoxymethyl methylol melamine, methoxymethyl ethoxymethylbenzoguanamine, tetrabutoxymethyl glycoluril, butoxymethyl methylol urea(up to 6%).

The above mentioned cross-linking can also be achieved usingpolycarbodiimides or multifunctional propylene imines.

It is also possible to blend one or more polymers having high cohesivestrength with one or more polymers having low cohesive strength in orderto achieve the desired balance.

Cross-linking is also important for effective switching and it istherefore necessary to distinguish between the type of cross-linkingthat is undertaken for controlling the cohesive strength of the adhesivecomposition and the type of cross-linking that brings about switching.In the first case, cross-linking for controlling the cohesive strengthof the adhesive is effected using an internal cross-linker, i.e., across-linker supplied with or forming part of the adhesive polymerbackbone material. In the second case, cross-linking for switching iseffected by visible light or UV-induced curing of the curable moleculesto form a three-dimensional polymeric network entangling the chains ofthe base adhesive polymer backbone, thereby reducing their mobility andfree volume. Preferably the amount of base adhesive polymer present inthe mixture is in the range 20% to 98% by weight, more preferably 40% to90% by weight, and most preferably 50% to 70% by weight. Preferably theproportion of curable molecules in the mixture ranges from 2% to 80% byweight, more preferably 10% to 60% by weight, and most preferably 30% to50% by weight. Preferably, the photoinitiator is present in the mixturein the proportions 0.1% to 5% by weight, more preferably 0.5% to 2% byweight. Preferably, the photoinitiator is also soluble in the drymixture of adhesive and curable molecules, although it will be capableof exerting its curing initiating effect upon exposure to an activatinglight source if finely dispersed through the dry mixture but notdissolved in it.

The weight proportion for the base adhesive polymer is given here interms of its dry weight and excludes any solvent which might normally bepresent in a commercially available bulk adhesive.

In certain embodiments, the weight proportion of base adhesive polymeris from one of the following lower endpoints (inclusive), or from one ofthe following upper endpoints (inclusive). The lower endpoints are 20%,30%, 40%, 50%, 60% and 70%; the upper endpoints are 98%, 95%, 90% and85%. In certain embodiments, the weight proportion of curable moleculesis from one of the following lower endpoints (inclusive), or from one ofthe following upper endpoints (inclusive). The lower endpoints are 2%,5%, 10% and 15%; the upper endpoints are 80%, 70%, 60%, 50%, 40% and30%. In certain embodiments, the weight proportion of photoinitiator isfrom one of the following lower endpoints (inclusive), or from one ofthe following upper endpoints (inclusive). The lower endpoints are0.05%, 0.1%, 0.2%, 0.5% and 1.0%; the upper endpoints are 10%, 5%, 4%and 3%.

The incidental constituents may be one or more of stabilizers,tackifiers, light scattering particles, fungicides, colorants,humectants, etc.

The adhesive component may be a hydrocolloid having polymeric chainsextending from a core or nucleus, and the reference to the adhesive andthe curable molecules being mutually soluble in each other when dry isto be understood as meaning that the curable molecules and the polymericchains are mutually soluble in each other. Hydrocolloid-based medicaldressings may be used for skin and wound treatment. When first attachedto the skin, dry hydrocolloids are only slightly adherent to the skin,but quickly absorb moisture from the skin and become more tacky.

The preparation method for the switchable adhesive compositions is verysimple. The adhesive component, the curable molecules (monomers and/oroligomers) and the photoinitiator are mixed, preferably stirred,together in darkness or under red light conditions for about 30 to 60minutes, most conveniently at room temperature. The mixture alsoincludes the internal cross-linker. The internal cross-linker may beincluded as part of the base adhesive, for example obtained from acommercial supplier who supplies as a stock item base adhesive withinternal cross-linkers. Alternatively, the internal cross-linker may besupplied as a separate component from the base adhesive. The internalcross-linker may be added to the mixture as a solution. The adhesivecomponent is usually supplied in solution (typically, 40% to 60% solidsby weight); the solvent for the adhesive may be a suitable vehicle fordissolving the internal cross-linker. The curable molecules are usuallysolvent free, although some curable molecules of high viscosity may becarried in a solvent which also could act to stabilize the internalcross-linker; the photoinitiator is usually solid and the most difficultcomponent of the system to dissolve and/or disperse.

Following completion of the mixing together, the resulting compositionis spread onto, e.g., a release liner at a certain thickness—typicallyabout 60 μm when wet—and then left to dry at room temperature for about10 minutes. The release liner may be a polyethylene coated paper with asilicone compound chemically bound to the surface. The spread adhesiveis then further dried at 80-150° C. for 3 to 10 minutes. A slightlyhigher temperature and a longer drying time can be used if necessary.After drying, the thickness of the spread adhesive will typically beabout 30 μm.

The dried adhesive is then transferred onto a carrier film, for example,for peel strength and switching evaluation.

Alternatively, the dried adhesive may be transferred to a material for awound dressing or an ostomy appliance, for example a web of polyethyleneor polyurethane film which may optionally be perforated, or a woven ornon-woven fabric.

For a medical dressing or similar application, the adhesive componentmay be selected from polymers capable of forming shaped bodies, thinwalls or coatings. Suitable polymers are biologically andpharmaceutically compatible, hypoallergenic and insoluble in andcompatible with body fluids or tissues with which the dressing iscontacted.

Exemplary light transmitting materials for carrying the adhesive polymerlayer include polyethylene, polypropylene, polyurethane,ethylene/propylene copolymers, ethylene/ethylacrylate copolymers,ethylene/vinyl acetate copolymers, silicone elastomers, especially themedical-grade polydimethylsiloxanes, neoprene rubber, polyisobutylene,polyacrylates, chlorinated poly-ethylene, polyvinyl chloride, vinylchloride-vinyl acetate copolymer, cross-linked polymethacrylate polymers(hydrogel), polyvinylidene chloride, poly(ethylene terephthalate), butylrubber, epichlorohydrin rubbers, ethylenevinyl alcohol copolymers,ethylene-vinyloxyethanol copolymers; silicone copolymers, for example,polysiloxane-polycarbonate copolymers, polysiloxanepolyethylene oxidecopolymers, polysiloxane-polymethacrylate copolymers,polysiloxane-alkylene copolymers (e.g., polysiloxane-ethylenecopolymers), polysiloxane-alkylenesilane copolymers (e.g.,polysiloxane-ethylenesilane copolymers), and the like; cellulosepolymers, for example methyl or ethyl cellulose, hydroxy propyl methylcellulose, and cellulose esters; polycarbonates;polytetrafluoro-ethylene; and the like.

The adhesives may be water-soluble, but will most often be soluble in,and hence commercially supplied as solutions in, organic solvents suchas ethyl acetate, hexane, toluene, acetone etc. Preferred adhesives arepolyacrylates, poly-urethanes and polysilicones. Especially preferredare polyacrylates. By the term polyacrylates is meant acrylate,methacrylate and acrylate copolymer adhesives. Indeed acrylate copolymeradhesives are most preferred, e.g. alkyl acrylate copolymers. The mostcommonly used monomers in polyacrylates are butyl acrylate, ethylhexylacrylate, hydroxyethyl acrylate and acrylic acid. They may be usedsingly or in a mixture, their relative proportions in the mixture beingselected depending on the water penetration rate, viscoelasticproperties, Tg, etc., that it is desired to achieve.

Cross-linking can be achieved by incorporating monomers of e.g.N-methylol acrylamide, N-(iso-butoxymethylene)acrylamide, methylacrylamidoglycolate methyl ether (all 0.5-5%) or metal chelates, e.g.,acetylacetonates of Zr, Al, or Fe (up to 2% of polymer weight) into thepolymer backbone which then cross-links during drying after spreading ona substrate.

Al and Ti acetylacetonates and similar compounds can also be added afterthe polymerization step in concentrations between 0.1 and 3% of thepolymer weight and used as an internal cross-linker through utilizingcarboxylic groups in the polymer backbone during the drying step.

Multi-functional isocyanates like TMDI, hexamethylene diisocyante, canbe used to chemically inter link hydroxylic or carboxylic functions ofdifferent polymer chains, added in concentrations up to 5%, for example1%, of the polymer weight.

Internal cross-linking can also be achieved between the carboxylicgroups in the polymer backbone and added amino resins such as melamine,benzoguanamine, glycoluril, urea derivatives e.g. hexamethoxymethylmelamine, methoxymethyl methylol melamine, methoxymethyl ethoxymethylbenzoguanamine, tetrabutoxymethyl glycoluril, butoxymethyl methylol urea(up to 6%).

The above mentioned cross-linking can also be achieved usingpolycarbodiimides or multifunctional propylene imines.

The backbone adhesive polymer used as the adhesive component of thecomposition must include a functional group that is able to reactchemically or physico-chemically with the internal cross-linker. It isalso possible to use, as the starting or base adhesive, one which ismanufactured with bound-in curable molecules; this is mixed with furthercurable molecules (not bound-in). The mechanism of internalcross-linking must not be a free radical mechanism because that is themechanism used for effecting cross-linking for the switching.

Preferably, the curable molecules and the adhesive are soluble in eachother when in the dry state, i.e., in the absence of a solvent.Alternatively, in the case that the adhesive and the curable moleculesare not mutually soluble in each other when dry, or are only partlymutually soluble, they are uniformly dispersed in the composition.Typically, the adhesive (or the base adhesive if a mixture of adhesivesis used) will be selected from polyacrylates, polyurethanes and siliconeadhesives.

In the broadest sense, any conventional known unsaturated compoundscould be used as the curable molecules, but preferred examples, usedalone or in mixtures, are curable molecules such as acrylic acid estersor methacrylic acid esters of alcohols, glycols, pentaerythritol,trimethylpropane, glycerol, aliphatic epoxides, aromatic epoxidesincluding bisphenol A epoxides, aliphatic urethanes, silicones,polyesters and polyethers, as well as ethoxylated or propoxylatedspecies thereof.

The curable molecules have more than one unsaturated site, i.e., greaterthan single functionality. Multiple functionalities of 3 or greater, ormore preferably 4 or greater are especially effective because curablemolecules of this type are able to form highly cross-linkedthree-dimensional polymeric networks which are an important feature ofswitching, as will be explained below. Also, many curable moleculeshaving multiple functionalities are commonly available at reasonablecost.

The radical initiator may be any species which is capable of producingradical species under the desired conditions but preferred examples arephotoinitiators able to start the radical reaction under mildconditions, e.g. visible light, in order to promote radicalpolymerization reactions in the curable molecules. As a consequence,when the photoinitiator becomes activated by exposure to visible light,the curable molecules form chemical bonds with other curable moleculesand hence create polymeric cross-linking. The effect of suchcross-linking is to build a three-dimensional polymeric networkentangling the adhesive polymer chains, thereby reducing their mobilityand free volume. The photoinitiator may alternatively produce radicalspecies under the mild conditions of long wave UV.

Curable molecules having multiple functionality are able to form highlycross-linked three-dimensional polymeric networks easily and henceexhibit good switching properties. The adhesive strength of the adhesivebecomes reduced and it becomes less tacky so that it may be peeled moreeasily from the surface to which it is attached.

The adhesive mixture preferably also contains stabilizers which areadded in order to prevent spontaneous cross-linking of the curablemolecules during storage. Examples of such stabilizers are hydroquinonessuch as 4-methoxy phenol (sometimes referred to as hydroquinonemonomethyl ether) and 2,4-ditert-butyl-metoxyphenol, or1-piperidinyloxy-4,4′-[1,10-dioxo-1,10-decanediyl)bis(oxy)]bis[2,2,6,6-tetramethyl] and pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate).

The adhesive mixture may also include photo-sensitisers. Since asensitising species often absorbs energy in a different part of thespectrum from the initiator, more effective use of the light source maybe achievable through the incorporation of sensitisers into the mixture.Many photo-sensitisers are complex organic molecules, absorbing in thevisible portion of the spectrum.

The adhesive mixture may also incorporate light scattering particles toincrease the effect of irradiation of the adhesive mixture. Preferably,the light scattering particles are an inorganic compound such as silicapowder, alumina powder, silica-alumina powder or mica powder withparticle sizes of the order of 10 nm or greater, typically up to 1 μm.

Any conventionally known free radical initiators may be used.Particularly preferred are those initiators which react to visible lightradiation, although initiators which react under shorter wavelengthlight may be used in the compositions, depending on the application.Thus, free radical initiators which may be mentioned include titanocenephotoinitiators; dye/co-initiator systems, e.g.,thionine/triethanol-amine; dye/borate salt systems; dye/peroxide systemsand 1,2-diketone/co-initiator systems, e.g., camphor-quinone/tertiaryamine.

Examples of visible light photoinitiators (which include Irgacure 784because it absorbs light both in the UV and visible spectrum) are:Benzildimethyl ketal; Phenanthrenequinone; Titanocenes (of whichIrgacure 784 is one example);Bis(2,4,6-trimethyl-benzoyl)-phenylphosphineoxide.

Examples of UV photoinitiators are: Benzoin and ethyl, isopropyl orisobutyl ethers of Benzoin; Benzophenone and hydroxy or methylbenzophenones;2-Methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one; Acetophenoneand 4′-Phenoxyacetophenone; Benzoyl-biphenyl; Benzil; Anisoin, as wellas the Irgacures such as Irgacure 651 (benzyl dimethyl ketal) orIrgacure 907(2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one); or theUvatones, such as Uvatone 8302 (2,2-diethoxy-1,2-diphenyl ethanone).

Preferred free radical photoinitiators for medical applications are thetitanocene initiators such asbis.(.eta.5-cyclopentadienyl)-bis(2,6-difluoro-3-[pyrrol-1-yl]-phenyl)titanium, sold in the UK by Ciba Geigy as Irgacure 784 (Trade Mark).

In embodiments, the second absorbent adhesive composition comprises apolymer comprising monomer units selected from the group consisting ofstyrene, isoprene, butadiene, ethylene, and butylene.

In embodiments, the second absorbent adhesive composition comprises astyrene block co-polymer.

In embodiments, the second absorbent adhesive composition comprises astyrene block co-polymer selected from the group consisting ofstyrene-isoprene-styrene (SIS), styrene-butadiene-styrene (SBS),styrene-isobutylene-styrene (SIBS), andstyrene-ethylene/butylene-styrene (SEBS).

In embodiments, the second absorbent adhesive composition comprises apolyethylene copolymer.

In embodiments, the second absorbent adhesive composition comprises apolyethylene copolymer selected from the group consisting of ethylenevinyl acetate, ethylene vinyl acetate carbon monoxide, ethylene butylacetate, ethylene vinyl alcohol, ethylene butyl acrylate, ethylene butylacrylate carbon monoxide, and combinations thereof.

In embodiments, the second absorbent adhesive composition comprisespolyisobutylene (PIB).

In embodiments, the absorbent adhesive composition may be switchable asdescribed herein for the switchable adhesive composition.

In embodiments, the second absorbent adhesive composition comprisesabsorbent material. In embodiments, the second absorbent adhesivecomposition comprises water absorbent material.

In embodiments, the second absorbent adhesive composition comprisesabsorbent material selected from the group consisting of hydrocolloids,microcolloids, salt, and super absorbent particles.

In embodiments, the absorbent adhesive composition comprises anabsorbent material in an amount of 1-60% (w/w) of the composition.

For instance, the absorbent adhesive composition comprises an absorbentmaterial in an amount of 1-40% (w/w) or 1-20% (w/w) or 20-40% (w/w) or20-60% (w/w) or 40-60% (w/w) or 25-50% (w/w) of the composition.

In embodiments, the absorbent material is selected from hydrocolloid,water soluble salt, mono, di- and oligosaccharides, sugar alcohols,polypeptides, organic acids, inorganic acids, amino acids, amines, urea,super absorbent particles such as polyacrylic acid, glycols such aspolyethylene glycol, fumed silica, bentone, bentonite, and mixturesthereof.

In embodiments, the hydrocolloid is selected from guar gum, locust beangum, pectin, potato starch, alginates, gelatine, xantan or gum karaya,cellulose derivatives, salts of carboxymethyl cellulose, sodiumcarboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose,hydroxyethyl cellulose, sodium starch glycolate, polyvinylalcohol, andmixtures thereof.

In embodiments, the water soluble salt is selected from NaCl, CaCl₂,K₂SO₄, NaHCO₃, Na₂CO₃, KCl, NaBr, NaI, KI, NH₄Cl, AlCl₃, CH₃COONa,CH₃COOK, HCOONa, HCOOK, and mixtures thereof.

In embodiments, the switchable and/or the absorbent adhesive compositionmay comprise ingredients such as tackifiers, extenders, non-reactivepolymers, oils (e.g. polypropyleneoxide, ethyleneoxide-propyleneoxidecopolymers, mineral oil), plasticizers, fillers, and surfactants.

In embodiments, the absorbent adhesive composition has an absorption ofat least 0.05 g/cm³/2 h, measured as described herein, such as anabsorption of at least 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5,0.6, 0.7, 0.8, 0.9, or 1 g/cm³/2 h measured as described herein.

In embodiments, the first switchable adhesive composition and/or thesecond absorbent adhesive composition has a moisture vapor transmissionrate (MVTR) above 250 g/m²/24 h measured as described herein, such asabove 500, 750, 1000, 1250, 1500, 2000, 2500, or 3000 g/m²/24 h measuredas described herein.

Moisture vapour transmission rate Moisture vapour transmission rate(MVTR) is measured in grams per square meter (g/m²) over a 24 hoursperiod using an inverted cup method.

A container or cup that was water and water vapour impermeable having anopening of 035 mm was used. 20 mL saline water (0.9% NaCl indemineralised water) was placed in the container and the opening wassealed with the test adhesive mounted on a highly permeable polyurethane(PU) backing film (BL9601 foil from Intellicoat). The container wasplaced into an electrically heated humidity cabinet and the container orcup was placed upside down, such that the water was in contact with theadhesive. The cabinet was maintained at 32° C. and 15% relative humidity(RH).

The weight loss of the container was followed as a function of time. Theweight loss was due to water transmitted through the adhesive and/orfilm. This difference was used to calculate the MVTR of the testadhesive film. MVTR was calculated as the weight loss per time dividedby the area of the opening in the cup (g/m²/24 h).

The MVTR of a material is a linear function of the thickness of thematerial. Thus, when reporting MVTR to characterize a material, it isimportant to inform the thickness of the material which MVTR wasreported. We used 150 μm as a reference. If thinner or thicker sampleswere measured, the MVTR was reported as corresponding to a 150 μmsample. Thus a 300 μm sample with a measured MVTR of 10 g/m²/24 h wasreported as having MVTR=20 g/m²/24 h for a 150 μm sample because of thelinear connection between thickness of sample and MVTR of sample.

Finally, we noted that by using this method, we introduced an error byusing a supporting PU film. Utilizing the fact that the adhesive/filmlaminate was a system of two resistances in series eliminated the error.When the film and the adhesive are homogeneous, the transmission ratemay be expressed as:

1/P(measured)=1/P(film)+1/P(adhesive).

Hence, by knowing the film permeability and thickness of the adhesive,it was possible to calculate the true permeability of the adhesive,P(adhesive), using the following expression:

P(adhesive)=d(adhesive)/150 μm*1/(1/P(measured)−1/P(film))

where d(adhesive) was the actual measured thickness of the adhesive andP(film) was the MVTR of the film without any adhesive on and P(measured)was the actual measured MVTR.

Moisture Absorption

Samples were prepared by thermoforming to a 0.5 mm thick adhesive filmbetween two release liners. With a punching tool, samples were punchedout. Sample size was 25×25 mm. The release liners were removed. Thesamples were glued to an object glass and placed in a beaker withphysiological salt water and placed in an incubator at 37° C.

The sample was weighed at the outset (M(start)) and after 2 hours (M(2hours). Before weighing, the object glass was dried off with a cloth.For a 25×25 mm sample the area was 6.25 cm² (the surface edges were leftout of the area). The moisture absorption may be calculated as: Waterabsorption after 2 hours=(M(2 hours)−M(start))/6.25 cm². The result isin the unit g/cm² per 2 hours.

Peel force Following the quantities and steps of a recipe, the compoundsare hand mixed in a dark glass recipient for 1-2 minutes. The mixturesare let to rest for 24 h before use, the necessary time for thecross-linker to dissolve.

Afterwards the solution is coated with a dog-bone coater (f ex. usingthe 500 μm thickness), on a siliconized paper used as a release liner(RL). Before use, or before addition of top film (that can bepolyurethane PU or polyethylene PE), the films are let for evaporationfor a long enough time (48-72 h). The final thickness of the samplesvaries between 120 and 170 μm.

When HC were added the same coating procedure is applied, only thethickness of the films will be different.

To perform peel tests 90°, the samples with top film added (PU or PE)were cut in rectangular shapes (25×100 mm) and a helping tape on top.For the uncured samples, an occlusive black film was added on top toprotect them from curing; also fast and in-the-dark handling wasperformed.

A sample of 25×100 mm2 was cut from the adhesive and firmly pressed onto a thoroughly cleaned plate (HDPE or TEFLON). A 25×300 mm2 piece ofauxiliary tape was then placed on the top of the adhesive and the wholesample pressure rolled to assure firm adhesion between the tape and theadhesive to be tested. After conditioning for 30 minutes at 23 plus orminus 3 degrees centigrade, the sample was mounted in a tensile testingmachine and a 90 degrees peel test was carried out at a speed of 304mm/min.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-section view of an adhesive wafer. In thisfigure, a first adhesive layer 2, provided on a backing layer 3 isoverlying a second adhesive 1. The lower surface of the adhesive waferis the surface that is in contact with the skin S of the user duringuse. This surface may be covered by a release liner (not illustrated),which is removed prior to adhering the wafer to the skin S. In FIG. 1,the lower surface of the adhesive wafer is constituted by the secondadhesive 1 covering the central portion of the surface and a firstadhesive 2 at a peripheral portion along the outer edge. The uppersurface is the surface facing away from the skin during use. Thissurface can be covered by a backing layer 3 to which a collecting bag 8is or can be attached. The adhesive wafer has a centrally locatedthrough-going hole 6 allowing output from the stoma 7 to pass into thecollecting bag 8. The second adhesive 1 is placed in the central part ofthe adhesive wafer, bordering the stoma 7 during use. The first adhesive2 can be a switchable adhesive composition as described herein. Thesecond adhesive 1 can be an absorbent adhesive composition as describedherein. The second adhesive 1 is bevelled along its outer periphery, sothe thickness of the central portion (the first thickness) of the secondadhesive is larger than the thickness of the peripheral portion (thesecond thickness) of the second adhesive 5. In this way, the spacevolume 4, defined by the skin S, the first 2 and the second adhesive 1is reduced or even eliminated as shown in FIG. 2. The first adhesive 2will adhere both to the distal surface of the second adhesive 1 as wellas to the sloping edge portion. Theoretically, the second thicknesscould be close to zero, but for practical reasons it is desired to havea rim portion 5 being substantially perpendicular to the plane of theadhesive layer, this perpendicular rim portion defining the secondthickness. The second thickness 5 defines the size of the space volume 4and the risk of delamination when peeling from skin S.

FIG. 2 is a schematic cross-section view of an adhesive wafer duringdetachment from the skin S. The skin S is here schematic shown as astraight line, but dependent of the strength of the adhesive as well asthe softness of the skin, it may in real life be pulled up a littlebefore detaching from the adhesive when the wafer is pulled away fromthe skin. When the wafer is detached at the edge portion and pulled awayfrom the skin (as shown with arrow on FIG. 2), first the first adhesivewill gradually detach from the skin, and after the space volume, thesecond adhesive begins to detach.

Embodiments, and features of the various exemplary embodiments describedin this application, may be combined with each other (“mixed andmatched”), unless specifically noted otherwise.

EXAMPLES Example 1

In order to test the differences in peel between peel from a stiffsubstrate versus peel from skin, the following test could be made:

A way of preparing a skin-like substrate could be the following:

Skin may differ in structure, dependent on for example age, gender andphysical condition of the person. In order to provide comparable andreproducible results, an artificial skin for testing peel on skin isprepared. The artificial skin is in the form of a soft silicone layer,covered with a soft film, as prepared as described below.

A soft skin-like substrate is prepared in order to simulate thestretching of skin when a product is removed. Casting of a 2 componentsilicone (84 g of Silgel 612 A and 66 g of Silgel 612 B) is carried outso that a soft 8-10 mm thick sticky silicone block is formed. The blockis cured for 1 hour at 70 degrees.

On top of the silicone is fixed a soft 30 μm Polyurethane film (PU,Scapa Bioflex 130), functioning as substrate for the tested adhesives.

For comparison, a stiff substrate is prepared by adhering the PU film(Scapa Bioflex 130) to a stiff HDPE plate with a standard acrylicdouble-sided adhesive (3M 1522).

For preparing test samples the following method could be used:

The hydrocolloid adhesive could be as follows:

A standard wear adhesive for ostomy care (Kraton 1161, from Kratonpolymers, Oppanol B12 from BASF. pectin LM CG, CP Kelco, Akucell AF288,Akzo Nobel, PB gelatine, PB Gelatins and Guar gum FG-20, Hercules Corp.is mixed in a z blade Austin 300 g mixer and applied vacuum) is pressedin to a 4 mm sheet. The sheet is bevelled from 4 mm to 0.05 mm over adistance of 11 mm giving an angle of bevelling of 20 degrees with theplane of the layer. The width of the bevelled edge is 80 mm. Thebevelled edge is cut in such a way that the bevelled edge is 50 μm inone end and 800 μm in the other end. In that way a graded bevelling withdifferent heights of bevelling from 3950 μm to 3200 μm is obtained. Theincreasing heights from 50 μm to 800 μm is used for determining when thehydrocolloid adhesive will come off together with the switched acrylicadhesive and when a delamination between the hydrocolloid adhesive andthe switchable adhesive may occur during peeling from skin and from astiff substrate. In FIG. 3 is shown a cross-section of the secondadhesive layer, with the first thickness X1 of the central portion andthe second thickness X2 of the edge portion. In FIG. 4 is shown the testsample of the second adhesive as described above.

The switchable adhesive could be as follows:

A BASF acResin A 260 UV with 1% photoinitiator is prepared by dissolving80 g BASF acResin A 260 UV in 120 mL toluene at room temperature using ashaker with a speed of 30 rpm. 60 g of the resulting solution is mixedwith 0.24 g Irgacure 784 photoinitiator using a spatula for 1 min. Theswitchable adhesive is provided in a layer of 60 μm thick and laminatedto a 25 μm PU film and the laminate is placed over the bevelled and cuthydrocolloid adhesive to form the test object simulating the deviceaccording to the invention. The switchable adhesive laminate extendfurther than the bevelled edge hydrocolloid adhesive.

Testing of Delamination During Peeling of Adhesive from Substrate

Testing of the test object is carried out at 20 degrees at 50% humidity.The test object is placed on the soft substrate and pressed on to itwith the finger to adhere. After 5 minutes, the switchable adhesive isswitched with a 365 nm UVA light source for 15 sec. The switchedadhesive is now only slightly adhesive and is peeled off with an angleof 90 degrees and a constant speed of approximately 1 cm/sec by hand(similar to the speed of normal removal of a ostomy product). The width(80 mm) of the graded bevelling front is peeled simultaneously. Theheight of the second thickness (X2) where the bevelled adhesives stoppeeling off the substrate together with the switchable adhesive andinstead delaminate is determined in μm by a Miotutoyo ocular. Threesamples are tested. The expected results are shown in Table 1. As can beseen from the table, the samples does not delaminate when peeled fromthe stiff substrate, whereas samples with a low second height (X2) ofthe bevelled edge tends to delaminate when peeled from the softsubstrate.

TABLE 1 Thickness before Sample Peel substrate delamination, μm 1 Softsilicone with soft PU film 300 2 Soft silicone with soft PU film 200 3Soft silicone with soft PU film 150 Average 217 bevelling 5 Stiff HDPEwith soft PU film +800 6 Stiff HDPE with soft PU film +800 7 Stiff HDPEwith soft PU film +800 Average +800 bevelling

The results of the test from Table 1 show that the bevelled hydrocolloidadhesive will follow the switchable adhesive when tested on a stiffsubstrate. When tested on a skin-like soft substrate, delamination ismuch more inclined to occur.

1. An ostomy device comprising: a backing layer comprising a distalsurface adapted to receive a waste collecting bag; a switchable adhesivelayer applied to a proximal surface of the backing layer, with theswitchable adhesive layer extending a first width to an outermostperimeter edge of the backing layer; and an absorbent adhesive layerapplied to a proximal surface of the switchable adhesive layer, with theabsorbent adhesive layer extending a peripheral distance that is lessthan the first width, and the absorbent adhesive layer comprises abevelled outer periphery such that a central portion of the absorbentadhesive layer is thicker than a peripheral portion measured along thebevelled outer periphery of the absorbent adhesive layer; wherein theswitchable adhesive layer is located between the backing layer and theabsorbent adhesive layer and covers an entirety of a distal surface ofthe surface of the absorbent adhesive layer; wherein the switchableadhesive layer comprises a photoinitiator reactive to visible light;wherein the absorbent adhesive layer is a skin-facing layer comprisingabsorbent particles.
 2. The ostomy device of claim 1, further comprisinga stoma hole formed through the backing layer, the switchable adhesivelayer, and the absorbent adhesive layer.
 3. The ostomy device of claim1, wherein the absorbent particles are distributed throughout theabsorbent adhesive layer.
 4. The ostomy device of claim 1, wherein theabsorbent particles are selected from the group consisting ofhydrocolloids, microcolloids, salt, and super absorbent particles. 5.The ostomy device of claim 1, wherein the switchable adhesive layer is aring-shaped annular band.
 6. The ostomy device of claim 1, wherein theswitchable adhesive layer comprises polyacrylate.
 7. The ostomy deviceof claim 1, wherein the switchable adhesive layer comprisespolyurethane.
 8. The ostomy device of claim 1, wherein the switchableadhesive layer comprises polysilicone.
 9. The ostomy device of claim 1,wherein the switchable adhesive layer comprises curable moleculesselected from the group consisting of acrylic acid esters or methacrylicacid esters of alcohols, glycols, pentaerythritol, trimethylpropane,glycerol, aliphatic epoxides, aromatic epoxides including bisphenol Aepoxides, aliphatic urethanes, silicones, polyesters and polyethers. 10.The ostomy device of claim 1, wherein the photoinitiator is selectedfrom the group consisting of titanocene photoinitiators;dye/co-initiator systems including thionine/triethanolamine; dye/boratesalt systems; dye/peroxide systems and 1,2-diketone/co-initiatorsystems, including camphor-quinone/tertiary amine.
 11. The ostomy deviceof claim 1, wherein the absorbent adhesive layer comprises monomer unitsselected from the group consisting of styrene, isoprene, butadiene,ethylene, and butylene.
 12. The ostomy device of claim 1, wherein theabsorbent adhesive layer comprises a styrene block co-polymer.
 13. Theostomy device of claim 1, wherein the absorbent adhesive layer comprisesa polyethylene copolymer.
 14. The ostomy device of claim 1, furthercomprising a waste collecting bag connected to the distal surface of thebacking layer.